For the efficient screening of drugs of abuse, simple but unambiguous analytical methods are required which can be performed on-site. This project is designed to develop an immunosensor for the detection of drugs of abuse. While the feasibility studies will be performed with cocaine and its major metabolite, benzoylecgonine, the sensor can be adapted to substances for which antibodies are available, including therapeutic drugs and other physiologically active compounds. Operation of the immunosensor does not require the usual procedures associated with immunoassays such as pipetting, adding to reagents, manual separation, mixing and the like but just dipping the disposable sensor into the biological medium (urine, blood, saliva). The generated signal will be monitored with existing technology as used for the measurement of blood glucose. The minimal time period for completing the assay is estimated to be between 3 and 5 minutes without the requirement to stop a reaction for completion.